The Application Of Digital Watermarking Scheme In Electronic Seal

With the rapid develop ment of the network technolo gy, the gover nment affa irsinformatio nizatio n has become a key research area to many countr ies. In recent years,the electronic seal techno logy has been deve loped significantly in China after theissue of the "Electronic Signature Law". As a result, how to make sure the infor mationuniq ueness, tamper-proofing and legitimac y have been the key issue of the electronicseal research. Digita l watermarking is an important way to achieve the goal. In thispaper, the research background of the e lectronic seal technolo gy, a long with the basicprinc ip le and applications of the digital water marking, is introduced. Two digita lwatermarking algorithms are then designed to achie ve the data integr ity and thecopyr ight protection require ments.First, a blind water marking a lgor ithm for data integr ity protection is designedwhich based on the chaos and dither quantizatio n DWT water marking a lgor ithm. Tosolve the problem that a carrier with d irectly embedded watermark is vulnerab le andlost infor mation, an a lgorithm whose watermark is scra mbled by chaos is proposed toimprove the attack resistance ability and increase its secrecy. Besides, the propertiesof the SVD method are also analyzed. Based on the SVD advanta ges, an approach,which embeds the watermark infor mation into the biggest singular value by dither ingquantization technolo gy, is introduced. Since the b lind water mark does not need theorigina l carrier invo lved in the extracted watermark require me nts, according to thesize of the water mark, adaptive wave let coeffic ie nts of low freque ncy of carr ier breakup, the water mark is e mbedded into the s ingular va lue of the corresponding block.Results show that blind watermark ing algor ithm has good robustness against thecommo n attack while poor robustness aga inst the ma lic ious attacks.Second, a non-blind watermarking a lgor ithm is designed based on the DWTima ge watermarking algorithm which is Zigzag scramb led for copyr ight protection.The inherent drawbacks of the Zigzag scra mbling is ana lyzed and m sequence isapplied to improve the Zigzag scramb ling. Exper iments have proved that the adaptedZigzag scra mbling has the advantages o f long cyc le and high scra mb ling degree. Toprotect the copyright, the water marking infor mation will be equally d istr ibuted in thelow frequenc y coeffic ient SVD matr ix o f the carr ier to improve the a lgor ithmrobustness. Results s how that non-blind watermark ing a lgor ithm has very strong robustness aga inst the common and ma lic ious attacks.Fina lly, a electronic seal syste m is designed. To meet the document unique nessand tamper-proofing require me nts, the MD5va lue is applied as watermark. Thesystem has two kinds of watermarking algor ithms: blind detectio n algor ithm of DWTwatermarking algor ithm based on the chaos and dither quantitative and non-blinddetection a lgorithm o f ima ge watermark ing a lgor ithm based on the improved Zigzagscramb ling DWT. According to the tests, the robustness of the DWT watermark ingalgor ithm based on chaos and dither quantization is weaker than the DWT imagewatermarking algor ithm based on improved Zigzag scramb ling, but the watermark canbe extracted without the origina l carrier partic ipation while the latter to extract moretrouble need the origina l carrier partic ipatio n; the for mer algor ithm is comp lex, thelatter method is simp le. Different algor ithms can be chosen according to the needs. Tosum up, the electronic seal s ystem has a good robustness, whic h bala nced thetradeoffs between invis ib ility and robustness. The bas ic design intent is achieved...